Secret to BGV to OpenFHE e2e pipeline

[j2kun]

This PR runs an end-to-end example (simple_sum) through the heir-simd-vectorizer pipeline, with the new bgv-add-client-interface, down to OpenFHE codegen, and runs the generated code in a test.

Deficiencies (still need to file TODOs):

• OpenFHE's MakePackedPlaintext will zero-pad to the ring degree N, and this breaks the rotate-and-reduce trick, so instead I have to manually repeat the coefficients cyclically until it fills the whole ciphertext. I'd like to add this to the encode helper, and it suggests a bunch more work to do if we have an input cleartext tensor that is not divisible by the OpenFHE's ring degree (rotate-and-reduce tricks won't work in that case, or will have to be tweaked to account for the true underlying ring degree).
• Support non-tensor input types to the encode codegen
• move int64_t casting to a higher-level lowering (say, from BGV to OpenFHE)

The output code generated for simple_sum

#include "src/pke/include/openfhe.h" // from @openfhe

using namespace lbcrypto;
using CiphertextT = ConstCiphertext<DCRTPoly>;
using CryptoContextT = CryptoContext<DCRTPoly>;
using EvalKeyT = EvalKey<DCRTPoly>;
using PlaintextT = Plaintext;
using PrivateKeyT = PrivateKey<DCRTPoly>;
using PublicKeyT = PublicKey<DCRTPoly>;

CiphertextT simple_sum(CryptoContextT v0, CiphertextT v1) {
  size_t v2 = 1;
  size_t v3 = 2;
  size_t v4 = 4;
  size_t v5 = 8;
  size_t v6 = 16;
  size_t v7 = 31;
  int64_t v8 = static_cast<int64_t>(v6);
  const auto& v9 = v0->EvalRotate(v1, v8);
  const auto& v10 = v0->EvalAdd(v1, v9);
  int64_t v11 = static_cast<int64_t>(v5);
  const auto& v12 = v0->EvalRotate(v10, v11);
  const auto& v13 = v0->EvalAdd(v10, v12);
  int64_t v14 = static_cast<int64_t>(v4);
  const auto& v15 = v0->EvalRotate(v13, v14);
  const auto& v16 = v0->EvalAdd(v13, v15);
  int64_t v17 = static_cast<int64_t>(v3);
  const auto& v18 = v0->EvalRotate(v16, v17);
  const auto& v19 = v0->EvalAdd(v16, v18);
  int64_t v20 = static_cast<int64_t>(v2);
  const auto& v21 = v0->EvalRotate(v19, v20);
  const auto& v22 = v0->EvalAdd(v19, v21);
  std::vector<int16_t> v23 = {0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1};
  std::vector<int64_t> v23_cast(std::begin(v23), std::end(v23));
  const auto& v24 = v0->MakePackedPlaintext(v23_cast);
  const auto& v25 = v0->EvalMult(v22, v24);
  int64_t v26 = static_cast<int64_t>(v7);
  const auto& v27 = v0->EvalRotate(v25, v26);
  const auto& v28 = v27;
  return v28;
}

CiphertextT simple_sum__encrypt(CryptoContextT v29, std::vector<int16_t> v30, PublicKeyT v31) {
  std::vector<int64_t> v30_cast(std::begin(v30), std::end(v30));
  const auto& v32 = v29->MakePackedPlaintext(v30_cast);
  const auto& v33 = v29->Encrypt(v31, v32);
  return v33;
}

int16_t simple_sum__decrypt(CryptoContextT v34, CiphertextT v35, PrivateKeyT v36) {
  PlaintextT v37;
  v34->Decrypt(v36, v35, &v37);
  int16_t v38 = v37->GetPackedValue()[0];
  return v38;
}

[j2kun]

OK this monster PR is working now, EXCEPT for one tiny detail: I can't figure out how to get the new //tests/openfhe/end_to_end:simple_sum_test to run with yosys enabled by default. It seems to run heir-opt with yosys dependencies missing by default, and to make it pass I have to run bazel test with --//:enable_yosys=0

Even if I run bazel test --//:enable_yosys=1 //tests/openfhe/end_to_end:simple_sum_test, it still complains that yosys deps/env vars are not found.

Edit: I think I understand now: the env variables set by the cc_binary build rule only apply when that target is bazel run, not when it is used in some other rule, nor when it is run from bazel-bin/. I will try to tweak that so that it can be used in all situations.

[asraa]

Thank you for all the fixes to the config settings and adding the compilation flag!

[j2kun]

Squashed and ready to pull